Page 377 - ILAE_Lectures_2015

Ictal. Arrhythmias, conduction block and repolarisation ECG abnormalities, such as atrial
fibrillation, marked sinus arrhythmia, supraventricular tachycardia, atrial and ventricular
premature depolarisation, bundle-branch block, high-grade atrioventricular conduction
block, ST segment depression and T wave inversion have been reported in up to 56% of
seizures. Abnormalities appear to be more common in nocturnal, prolonged and generalised
seizures than in focal seizures or those occurring during wakefulness44,67-70.

Sinus rate change is the most common cardiac accompaniment to ictal discharge. Sinus
tachycardia has been reported in 50100% of seizures, and is dependent on the definition
used and population studied58-60,70-76. Although the heart rate in ictal tachycardia is typically
100120 beats per minute58, there are reports of rates exceeding 170 beats per minute, even
during simple partial seizures59,71. Ictal tachycardia is most commonly seen in the early ictal
phase, soon after seizure onset71,73,75,76, or rarely before clear evidence of electroclinical
onset70. This contrasts with ictal bradycardia which is seen during the late ictal phase or in
the immediate post-ictal period77,78. There is some evidence for right-sided lateralisation and
temporal lobe localisation in patients with ictal tachycardia72,73,76, corroborating the reports
of early experimental and clinical stimulation studies79,80,81, although it is important to note
that most temporal lobe seizures are associated with ictal tachycardia, irrespective of
lateralisation. In contrast, in patients with unilateral temporal lobe epilepsy being evaluated
with extensive intracranial EEG electrodes, irrespective of lateralisation of ictal onset, heart
rate was seen to increase incrementally as new cortical regions anywhere in the brain were
recruited82.

Although ictal tachycardia is almost universally observed, ictal bradycardia has received
more attention due to the potential progression to cardiac asystole and intuitive but unproven
association with SUDEP.

The first report of ictal asystole was by Russell in 1906, who noted the disappearance of a
young male patient’s pulse during a seizure83. The published literature since that time is,
unsurprisingly, mostly case reports or small series studies, which significantly limit the
number and confidence of any conclusions extracted from the data. Ictal bradycardia is
observed in <5% of recorded seizures59,73,75,84, but may occur in a higher percentage of
patients, because a consistent cardiac response to each apparently electroclinically identical
seizure is not seen59.

A recent literature review revealed that of 65 cases of ictal bradycardia with sufficient EEG
and ECG data, seizure onset was localised to the temporal lobe in 55%, the frontal lobe in
20%, the frontotemporal region in 23%, and the occipital lobe in 2%. Information regarding
seizure-onset lateralisation was available in 56 cases. Seizure onset was lateralised to the left
hemisphere in 63%, the right in 34%, and bilaterally in 4%. Interestingly, of 22 cases with
EEG data available at the onset of the bradycardia, 12 showed bilateral hemispheric ictal
activity, while six showed left-sided, and four showed right-sided activity78. No control group
data is available however. Nevertheless, it appears that there is a trend towards the left
temporal lobe being implicated in ictal bradycardia, however this is not sufficiently specific
to be valuable localising semiological information78,84.

Ictal asystole, lasting between 4 and 60 seconds, is reported, albeit rarely, in patients with
refractory epilepsy40,59,70,85-87. In addition, experimental data suggests that ictal
bradyarrhythmias can lead to complete heart block64. Short periods of EEG/ECG monitoring
may underestimate the prevalence of ictal asystole. For example, evaluation of a database of
6825 patients undergoing inpatient video-EEG monitoring found ictal asystole in only 0.27%
of all patients with epilepsy. In contrast, a study reported on 19 patients with refractory focal
epilepsy who were implanted with an ECG loop recorder for up to 18 months. Over 220,000